steam boiler

I got a gas fired steam boiler and when we purchased the house the last owner told us to change the water in the boiler once per year.

but one of my friend said with steam i should just add water whenever the water is below 30% on the sight glass mark but no need to change out the old water. But if that is true why is there a drain valve on the boiler than?

so should I change out the old water in the boiler? If so how often?
thanks.

The drain valve is on the boiler, the same as every other vessel, so the water can be drained if necessary. What is important to flush periodically is the low water cutoff float chamber. If material builds up in it the float will not drop when it has to and that will negate the LWC's safety function.

The drain valve is on the boiler, the same as every other vessel, so the water can be drained if necessary. What is important to flush periodically is the low water cutoff float chamber. If material builds up in it the float will not drop when it has to and that will negate the LWC's safety function.